1. Field of the Invention
This invention relates to an apparatus for manufacturing annular or tubular workpieces from concrete, comprising molding means, which have a vertical axis and between a core and a shell, which surrounds and is radially spaced from the core, define a mold cavity, which is adapted to be filled with concrete from above, feeding and distributing means, which are radially guided relative to the molding means and serve to feed and distribute the concrete which is to be dispensed into the mold cavity, and a molding press, which comprises a vertical ram that carries a molding ring, which is adapted to close the mold cavity at its top, and which press is radially displaceable relative to the molding means.
2. Description of the Prior Art
In apparatuses of that kind the mold cavity of the molding means is filled with concrete by means of the feeding and distributing means before the top end face of the workpiece can be molded in that a molding ring is forced into the annular gap between the core and the shell of the molding means. For that purpose the feeding and distributing means must first be retracted from their operative position in order to provide a space for the molding press, which carries the molding ring. That molding press is subsequently displaced or pivotally moved to a position over the molding means. When it is desired to remove the workpiece from the mold cavity the molding press must be returned to its initial position so that the workpiece can be axially extracted upwardly from the molding means, usually together with the shell, by means of an extracting crane. To minimize the space required for the feeding and distributing means it is known (German Patent Specitication 37 04 881) to arrange the feeding and distributing means for the concrete and the molding press one over the other and to displaceably mount them in a common frame so that the feeding and distributing means and the molding press can individually be displaced to the operative position over the molding means and back to the initial position as is required in the sequence of operations. But that known apparatus for manufacturing annular or tubular workpieces from concrete has the disadvantage that owing to the fact that the molding press is disposed above the feeding and distributing means the ram of the press must perform relatively large strokes and the forces exerted by the press must be taken up by the frame, which supports the molding press as well as the feeding and distributing means, so that heavy structures are required for that frame and for the carriage which carries the press. Besides, the separate drive means required to displace the feeding and distributing means, on the one hand, and the molding press, on the other hand, and the separate means for controlling said displacements involve a high structural expenditure.